U.S. patent application number 13/671027 was filed with the patent office on 2013-05-09 for wireless power transmission system and method based on impedance matching condition.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. The applicant listed for this patent is Jin Sung CHOI, Dong Zo KIM, Ki Young KIM, Nam Yun KIM, Sang Wook KWON, Eun Seok PARK, Yun Kwon PARK, Young Ho RYU, Keum Su SONG, Chang Wook YOON. Invention is credited to Jin Sung CHOI, Dong Zo KIM, Ki Young KIM, Nam Yun KIM, Sang Wook KWON, Eun Seok PARK, Yun Kwon PARK, Young Ho RYU, Keum Su SONG, Chang Wook YOON.
Application Number | 20130113298 13/671027 |
Document ID | / |
Family ID | 48223218 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130113298 |
Kind Code |
A1 |
RYU; Young Ho ; et
al. |
May 9, 2013 |
WIRELESS POWER TRANSMISSION SYSTEM AND METHOD BASED ON IMPEDANCE
MATCHING CONDITION
Abstract
A wireless power transmission system and a method based on an
impedance matching condition are provided. A source device of the
wireless power transmission system, includes a power converter
configured to generate power. The source device further includes a
resonator configured to transmit the power to a target device. A
ratio of an input impedance of the resonator to an output impedance
of the power converter is less than a reference value.
Inventors: |
RYU; Young Ho; (Yongin-si,
KR) ; PARK; Eun Seok; (Yongin-si, KR) ; KWON;
Sang Wook; (Seongnam-si, KR) ; KIM; Ki Young;
(Yongin-si, KR) ; KIM; Nam Yun; (Seoul, KR)
; KIM; Dong Zo; (Yongin-si, KR) ; PARK; Yun
Kwon; (Dongducheon-si, KR) ; SONG; Keum Su;
(Seoul, KR) ; YOON; Chang Wook; (Seoul, KR)
; CHOI; Jin Sung; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RYU; Young Ho
PARK; Eun Seok
KWON; Sang Wook
KIM; Ki Young
KIM; Nam Yun
KIM; Dong Zo
PARK; Yun Kwon
SONG; Keum Su
YOON; Chang Wook
CHOI; Jin Sung |
Yongin-si
Yongin-si
Seongnam-si
Yongin-si
Seoul
Yongin-si
Dongducheon-si
Seoul
Seoul
Seoul |
|
KR
KR
KR
KR
KR
KR
KR
KR
KR
KR |
|
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
48223218 |
Appl. No.: |
13/671027 |
Filed: |
November 7, 2012 |
Current U.S.
Class: |
307/104 |
Current CPC
Class: |
Y02T 10/7072 20130101;
H02J 50/80 20160201; B60L 53/65 20190201; H02J 7/025 20130101; B60L
53/38 20190201; Y02T 90/16 20130101; Y02T 10/72 20130101; B60L
53/126 20190201; Y02T 90/167 20130101; Y04S 30/14 20130101; H02J
50/90 20160201; Y02T 90/14 20130101; H02J 50/40 20160201; H01F
38/14 20130101; H02J 50/12 20160201; B60L 2210/40 20130101; Y02T
90/12 20130101; B60L 2210/30 20130101; H02J 7/00034 20200101; B60L
53/36 20190201; Y02T 10/70 20130101 |
Class at
Publication: |
307/104 |
International
Class: |
H01F 38/14 20060101
H01F038/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2011 |
KR |
10-2011-0116026 |
Claims
1. A source device of a wireless power transmission system, the
source device comprising: a power converter configured to generate
power; and a resonator configured to transmit the power to a target
device, wherein a ratio of an input impedance of the resonator to
an output impedance of the power converter is less than a reference
value.
2. The source device of claim 1, wherein: the reference value is
determined based on a power transmission efficiency of the wireless
power transmission system.
3. The source device of claim 1, further comprising: a matching
network configured to perform impedance matching between the
resonator and the target device based on a change in an impedance
between the resonator and the target device.
4. The source device of claim 1, further comprising: a matching
network configured to perform impedance matching between the
resonator and the target device to maintain a value of a voltage
standing wave ratio (VSWR) between the resonator and the target
device to be less than 2.
5. The source device of claim 1, wherein: the reference value is
greater than 0.5, and is less than 2.
6. The source device of claim 1, further comprising: a matching
network configured to perform impedance matching between the
resonator and the target device, wherein in an initial condition,
the matching network is further configured to maintain the input
impedance of the resonator in a first quadrant or a fourth quadrant
of a Smith chart, and the initial condition indicates that the
target device is recognized to be in an open state.
7. A source device of a wireless power transmission system, the
source device comprising: a power converter configured to generate
a power; a resonator configured to transmit the power to target
devices; and a matching network configured to perform impedance
matching between the resonator and the target devices, wherein a
ratio of an input impedance of the resonator to an output impedance
of the power converter is less than a reference value.
8. A target device of a wireless power transmission system, the
target device comprising: a resonator configured to receive and
output power from a source device; and a rectification unit
configured to rectify the power output from the resonator, wherein
a ratio of an output impedance of the resonator to an input
impedance of the rectification unit is less than a reference
value.
9. The target device of claim 8, wherein: the reference value is
determined based on a power transmission efficiency of the wireless
power transmission system.
10. The target device of claim 8, further comprising: a matching
network configured to perform impedance matching between the
resonator and the source device based on a change in an impedance
between the resonator and the source device.
11. The target device of claim 8, further comprising: a matching
network configured to perform impedance matching between the
resonator and the source device to maintain a value of a voltage
standing wave ratio (VSWR) between the resonator and the source
device to be less than 2.
12. The target device of claim 8, wherein: the reference value is
greater than 0.5, and is less than 2.
13. A power transmission method of a wireless power transmission
system, the power transmission method comprising: generating, by a
power converter, a power; and transmitting, by a resonator, the
power to a target device, wherein a ratio of an input impedance of
the resonator to an output impedance of the power converter is less
than a reference value.
14. The power transmission method of claim 13, further comprising:
performing impedance matching between the resonator and the target
device based on a change in an impedance between the resonator and
the target device.
15. The power transmission method of claim 13, further comprising:
performing impedance matching between the resonator and the target
device to maintain a value of a voltage standing wave ratio (VSWR)
between the resonator and the target device to be less than 2.
16. The power transmission method of claim 13, wherein: the
reference value is greater than 0.5, and is less than 2.
17. The power transmission method of claim 13, further comprising:
performing impedance matching between the resonator and the target
device; and maintaining, in an initial condition, the input
impedance of the resonator in a first quadrant or a fourth quadrant
of a Smith chart, wherein the initial condition indicates that the
target device is recognized to be in an open state.
18. A power transmission method of a wireless power transmission
system, the power transmission method comprising: generating, by a
power converter, a power; transmitting, by a resonator, the power
to target devices; and performing impedance matching between the
resonator and the target devices, wherein a ratio of an input
impedance of the resonator to an output impedance of the power
converter is less than a reference value.
19. A power reception method of a wireless power transmission
system, the power reception method comprising: receiving, by a
resonator, a power from a source device; and rectifying, by a
rectification unit, the received power, wherein a ratio of an
output impedance of the resonator to an input impedance of the
rectification unit is less than a reference value.
20. The power reception method of claim 19, further comprising:
performing impedance matching between the resonator and the source
device based on a change in an impedance between the resonator and
the source device.
21. The power reception method of claim 19, further comprising:
performing impedance matching between the resonator and the source
device to maintain a value of a voltage standing wave ratio (VSWR)
between the resonator and the source device to be less than 2.
22. The power reception method of claim 19, wherein: the reference
value is greater than 0.5, and is less than 2.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(a) of Korean Patent Application No. 10-2011-0116026,
filed on Nov. 8, 2011, in the Korean Intellectual Property Office,
the entire disclosure of which is incorporated herein by reference
for all purposes.
BACKGROUND
[0002] 1. Field
[0003] The following description relates to a wireless power
transmission system and a method based on an impedance matching
condition.
[0004] 2. Description of Related Art
[0005] Wireless power refers to energy transferred from a wireless
power transmitter to a wireless power receiver, for example,
through magnetic coupling. A wireless power transmission system
includes a source device and a target device. The source device
wirelessly transmits power, and the target device wirelessly
receives the power. The source device may be referred to as a
wireless power transmitter, and the target device may be referred
to as a wireless power receiver.
[0006] The source device includes a source resonator, and the
target device includes a target resonator. Magnetic coupling or
resonance coupling may be formed between the source resonator and
the target resonator.
[0007] Due to characteristics of a wireless environment, a distance
between a source device and a target device, or matching conditions
to match a source resonator and a target resonator, may be changed,
which may result in a change in a power transmission efficiency.
Accordingly, there is a desire for a wireless power transmission
system that maintains the power transmission efficiency.
SUMMARY
[0008] In one general aspect, there is provided a source device of
a wireless power transmission system, the source device including a
power converter configured to generate power. The source device
further includes a resonator configured to transmit the power to a
target device. A ratio of an input impedance of the resonator to an
output impedance of the power converter is less than a reference
value.
[0009] The reference value may be determined based on a power
transmission efficiency of the wireless power transmission
system.
[0010] The source device may further include a matching network
configured to perform impedance matching between the resonator and
the target device based on a change in an impedance between the
resonator and the target device.
[0011] The source device may further include a matching network
configured to perform impedance matching between the resonator and
the target device to maintain a value of a voltage standing wave
ratio (VSWR) between the resonator and the target device to be less
than 2.
[0012] The reference value may be greater than 0.5, and may be less
than 2.
[0013] The source device may further include a matching network
configured to perform impedance matching between the resonator and
the target device. In an initial condition, the matching network
may be further configured to maintain the input impedance of the
resonator in a first quadrant or a fourth quadrant of a Smith
chart. The initial condition may indicate that the target device is
recognized to be in an open state.
[0014] In another general aspect there is provided a source device
of a wireless power transmission system, the source device
including a power converter configured to generate a power. The
source device further includes a resonator configured to transmit
the power to target devices. The source device further includes a
matching network configured to perform impedance matching between
the resonator and the target devices. A ratio of an input impedance
of the resonator to an output impedance of the power converter is
less than a reference value.
[0015] In still another general aspect, there is provided a target
device of a wireless power transmission system, the target device
including a resonator configured to receive and output power from a
source device. The target device further includes a rectification
unit configured to rectify the power output from the resonator. A
ratio of an output impedance of the resonator to an input impedance
of the rectification unit is less than a reference value.
[0016] The target device may further include a matching network
configured to perform impedance matching between the resonator and
the source device based on a change in an impedance between the
resonator and the source device.
[0017] The target device may further include a matching network
configured to perform impedance matching between the resonator and
the source device to maintain a value of a voltage standing wave
ratio (VSWR) between the resonator and the source device to be less
than 2.
[0018] In yet another general aspect, there is provided a power
transmission method of a wireless power transmission system, the
power transmission method including generating, by a power
converter, a power. The method further includes transmitting, by a
resonator, the power to a target device. A ratio of an input
impedance of the resonator to an output impedance of the power
converter is less than a reference value.
[0019] The method may further include performing impedance matching
between the resonator and the target device based on a change in an
impedance between the resonator and the target device.
[0020] The method may further include performing impedance matching
between the resonator and the target device to maintain a value of
a voltage standing wave ratio (VSWR) between the resonator and the
target device to be less than 2.
[0021] The method may further include performing impedance matching
between the resonator and the target device. The method may further
include maintaining, in an initial condition, the input impedance
of the resonator in a first quadrant or a fourth quadrant of a
Smith chart.
[0022] In another general aspect, there is provided a power
transmission method of a wireless power transmission system, the
power transmission method including generating, by a power
converter, a power. The method further includes transmitting, by a
resonator, the power to target devices. The method further includes
performing impedance matching between the resonator and the target
devices. A ratio of an input impedance of the resonator to an
output impedance of the power converter is less than a reference
value.
[0023] In still another general aspect, there is provided a power
reception method of a wireless power transmission system, the power
reception method including receiving, by a resonator, a power from
a source device. The method further includes rectifying, by a
rectification unit, the received power. A ratio of an output
impedance of the resonator to an input impedance of the
rectification unit is less than a reference value.
[0024] The method may further include performing impedance matching
between the resonator and the source device based on a change in an
impedance between the resonator and the source device.
[0025] The method may further include performing impedance matching
between the resonator and the source device to maintain a value of
a voltage standing wave ratio (VSWR) between the resonator and the
source device to be less than 2.
[0026] Other features and aspects will be apparent from the
following detailed description, the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a diagram illustrating an example of a wireless
power transmission system.
[0028] FIG. 2 is a diagram illustrating an example of a
multi-target environment.
[0029] FIGS. 3 through 5 are diagrams illustrating examples of
schemes of adjusting an impedance between a source resonator and a
target resonator.
[0030] FIGS. 6A and 6B are diagrams illustrating an example of a
wireless power transmitter.
[0031] FIG. 7A is a diagram illustrating an example of a
distribution of a magnetic field within a source resonator based on
feeding of a feeding unit.
[0032] FIG. 7B is a diagram illustrating examples of equivalent
circuits of a feeding unit and a source resonator.
[0033] FIGS. 8 and 9 are diagrams illustrating examples of
impedance matching of a wireless power transmission system.
[0034] FIG. 10 is a diagram illustrating an example of a matching
network of a wireless power transmission system.
[0035] FIG. 11 is a diagram illustrating an example of a Smith
chart to describe an impedance matching condition of a wireless
power transmission system.
[0036] FIG. 12 is a diagram illustrating an example of an electric
vehicle charging system.
[0037] FIGS. 13A through 14B are diagrams illustrating examples of
applications in which a wireless power transmitter and a wireless
power receiver are mounted.
[0038] FIG. 15 is a diagram illustrating an example of a wireless
power transmitter and a wireless power receiver.
[0039] Throughout the drawings and the detailed description, unless
otherwise described, the same drawing reference numerals will be
understood to refer to the same elements, features, and structures.
The relative size and depiction of these elements may be
exaggerated for clarity, illustration, and convenience.
DETAILED DESCRIPTION
[0040] The following detailed description is provided to assist the
reader in gaining a comprehensive understanding of the methods,
apparatuses, and/or systems described herein. Accordingly, various
changes, modifications, and equivalents of the systems,
apparatuses, and/or methods described herein will be suggested to
those of ordinary skill in the art. The progression of processing
steps and/or operations described is an example; however, the
sequence of steps and/or operations is not limited to that set
forth herein and may be changed as is known in the art, with the
exception of steps and/or operations necessarily occurring in a
certain order. Also, description of well-known functions and
constructions may be omitted for increased clarity and
conciseness.
[0041] FIG. 1 illustrates an example of a wireless power
transmission system. Referring to FIG. 1, the wireless power
transmission and charging system includes a source device 110 and a
target device 120. The source device 110 is a device supplying
wireless power, and may be any of various devices that supply
power, such as pads, terminals, televisions (TVs), and any other
device that supplies power. The target device 120 is a device
receiving wireless power, and may be any of various devices that
consume power, such as terminals, TVs, vehicles, washing machines,
radios, lighting systems, and any other device that consumes
power.
[0042] The source device 110 includes an alternating
current-to-direct current (AC/DC) converter 111, a power detector
113, a power converter 114, a control and communication
(control/communication) unit 115, and a source resonator 116.
Additionally, the source device 110 further includes a matching
network 117.
[0043] The target device 120 includes a target resonator 121, a
rectification unit 122, a DC-to-DC (DC/DC) converter 123, a switch
unit 124, a device load 125, and a control/communication unit 126.
Furthermore, the target device 120 further includes a matching
network 127.
[0044] The AC/DC converter 111 generates a DC voltage by rectifying
an AC voltage having a frequency of tens of hertz (Hz) output from
a power supply 112. The AC/DC converter 111 may output a DC voltage
having a predetermined level, or may output a DC voltage having an
adjustable level by the control/communication unit 115.
[0045] The power detector 113 detects an output current and an
output voltage of the AC/DC converter 111, and provides, to the
control/communication unit 115, information on the detected current
and the detected voltage. Additionally, the power detector 113
detects an input current and an input voltage of the power
converter 114.
[0046] The power converter 114 generates a power by converting the
DC voltage output from the AC/DC converter 111 to an AC voltage
using a switching pulse signal having a frequency of a few
kilohertz (kHz) to tens of megahertz (MHz). In other words, the
power converter 114 converts a DC voltage supplied to a power
amplifier to an AC voltage using a reference resonance frequency
F.sub.Ref, and generates a wake-up power to be used for activating
or a charging power to be used for charging that may be used in a
plurality of target devices. The wake-up power may be, for example,
a low power of 0.1 to 1 milliwatts (mW) that may be used by a
target device to perform communication, and the charging power may
be, for example, a high power of 1 mW to 200 Watts (W) that may be
consumed by a device load of a target device. In this description,
the term "charging" may refer to supplying power to an element or a
unit that charges a battery or other rechargeable device with
power. Also, the term "charging" may refer supplying power to an
element or a unit that consumes power. For example, the term
"charging power" may refer to power consumed by a target device
while operating, or power used to charge a battery of the target
device. The unit or the element may include, for example, a
battery, a display device, a sound output circuit, a main
processor, and various types of sensors.
[0047] A ratio of an input impedance of the source resonator 116 to
an output impedance of the power converter 114 may be less than a
reference value. The reference value may be determined based on a
charging power transmission efficiency. To maintain the charging
power transmission efficiency above 90%, the reference value may
need to be greater than 0.5 and less than 2. Hereinafter, the ratio
of the input impedance of the source resonator 116 to the output
impedance of the power converter 114 may be referred to as an
impedance transformation ratio (ITR).
[0048] The output impedance of the power converter 114 may refer to
an impedance viewed in a direction from the matching network 117 to
the power converter 114, as indicated by an arrow 101 of FIG. 1.
Additionally, the input impedance of the source resonator 116 may
refer to an impedance viewed in a direction from the matching
network 117 to the source resonator 116, as indicated by an arrow
102 of FIG. 1.
[0049] The control/communication unit 115 may detect a reflected
wave of the communication power or a reflected wave of the charging
power, and may detect mismatching between the target resonator 121
and the source resonator 116 based on the detected reflected wave.
The control/communication unit 115 may detect the mismatching by
detecting an envelope of the reflected wave, or by detecting an
amount of a power of the reflected wave. The control/communication
unit 115 may calculate a voltage standing wave ratio (VSWR) based
on a voltage level of the reflected wave and a level of an output
voltage of the source resonator 116 or the power converter 114.
When the VSWR is greater than a predetermined value, the
control/communication unit 115 detects the mismatching.
[0050] Also, the control/communication unit 115 may control a
frequency of a switching pulse signal used by the power converter
114.
[0051] The control/communication unit 115 may perform out-of-band
communication using a communication channel. The
control/communication unit 115 may include a communication module,
such as a ZigBee module, a Bluetooth module, or any other
communication module, that the control/communication unit 115 may
use to perform the out-of-band communication. The
control/communication unit 115 may transmit or receive data to or
from the target device 120 via the out-of-band communication.
[0052] The source resonator 116 transfers electromagnetic energy,
such as the communication power or the charging power, to the
target resonator 121 via a magnetic coupling with the target
resonator 121.
[0053] The matching network 117 performs impedance matching between
the source resonator 116 and the target device 120. A
characteristic of the matching network 117 will be further
described with reference to FIGS. 8 through 10.
[0054] The target resonator 121 receives the electromagnetic
energy, such as the wake-up power or the charging power, from the
source resonator 116 via a magnetic coupling with the source
resonator 116. The wake-up power is used to activate a
communication function and a control function, and the charging
power is used to perform charging.
[0055] The matching network 127 performs impedance matching between
the target resonator 121 and the source device 110. A
characteristic of the matching network 127 will be further
described with reference to FIGS. 8 through 10.
[0056] The rectification unit 122 (i.e., a rectifier) generates a
DC voltage by rectifying an AC voltage received by the target
resonator 121.
[0057] A ratio of an output impedance of the target resonator 121
to an input impedance of the rectification unit 122 may be less
than a reference value. The reference value may be determined based
on the charging power transmission efficiency.
[0058] The input impedance of the rectification unit 122 may refer
to an impedance viewed in a direction from the matching network 127
to the rectification unit 122, as indicated by an arrow 104 of FIG.
1. The output impedance of the target resonator 121 may refer to an
impedance viewed in a direction from the matching network 127 to
the target resonator 121, as indicated by an arrow 103 of FIG.
1.
[0059] The DC/DC converter 123 adjusts a level of the DC voltage
output from the rectification unit 122 based on a voltage rating of
the device load 125. For example, the DC/DC converter 123 may
adjust the level of the DC voltage output from the rectification
unit 122 to a level in a range from 3 volts (V) to 10 V.
[0060] The switch unit 124 is turned on or off by the
control/communication unit 126. When the switch unit 124 is turned
off, the control/communication unit 115 of the source device 110
may detect a reflected wave. In other words, when the switch unit
124 is turned off, the magnetic coupling between the source
resonator 116 and the target resonator 121 is interrupted.
[0061] The device load 125 may include, for example, a battery, a
display, a sound output circuit, a main processor, and/or various
sensors. The device load 125 may charge the battery using the DC
voltage output from the DC/DC converter 123.
[0062] The control/communication unit 126 is activated by the
wake-up power. The control/communication unit 126 communicates with
the source device 110, and controls an operation of the target
device 120.
[0063] The rectification unit 122, the DC/DC converter 123, and the
switch unit 124 of FIG. 1 may be referred to as power supply units.
Accordingly, the target device 120 may include the target resonator
121 and the power supply units 122, 123 and 124 configured to
supply the received power to the device load 125. The device load
125 may be expressed as a load.
[0064] FIG. 2 illustrates an example of a multi-target environment.
Referring to FIG. 2, a source device 210 simultaneously, wirelessly
transfers energy and data to target devices, for example, target
devices 221, 223, and 225. That is, based on a wireless power
transmission employing a resonance scheme, the source device 210
simultaneously charges the target devices 221, 223, and 225.
[0065] The source device 210 may include the same structure as the
source device 110 of FIG. 1. Additionally, each of the target
devices 221, 223 and 225 may include the same structure as the
target device 120 of FIG. 1.
[0066] A source resonator of the source device 210 transmits
charging power to the target devices 221, 223 and 225.
Additionally, a matching network of the source device 210
adaptively performs impedance matching between the source resonator
and the target devices 221, 223 and 225.
[0067] The target devices 221, 223, and 225 may be of various
types. For example, the target device 221 may be a smartphone, a
tablet personal computer (PC), and/or an MP3 (Moving Picture
Experts Group Audio Layer III) player. Additionally, the target
devices 223 and 225 may be of the same type as, or a different type
from, the target device 221.
[0068] In a single target environment (e.g., of FIG. 1), an
impedance between a source resonator and a target resonator may be
changed based on, for example, a distance between the source
resonator and the target resonator, an angle formed by the source
resonator and the target resonator, a relative position of the
target resonator with respect to the source resonator, and/or other
factors known to one of ordinary skill in the art. Additionally,
while the single target environment is changed to a multi-target
environment (e.g., of FIG. 2), an impedance between a source
resonator and target resonators may be changed. The change in the
impedance may be closely-related to a total efficiency of a
wireless power transmission system.
[0069] In the single target environment and the multi-target
environment, to obtain an optimum power transmission efficiency, at
least one of three conditions described below may need to be
satisfied.
[0070] [Condition 1]
[0071] A value of an ITR of a source device and/or a target device
is designed or predetermined to be close to 1. For example, the
value of the ITR may be greater than 0.5 and less than 2. Condition
1 will be further described with reference to FIG. 10.
[0072] [Condition 2]
[0073] A value of a voltage stranding wave ratio (VSWR) between a
source resonator and a target device is maintained to be less than
2. Condition 2 will be further described with reference to FIGS. 3
through 9.
[0074] [Condition 3]
[0075] In an initial condition, a matching network of a source
device is designed or configured so that a large amount of power is
transferred to a target device. The initial condition may indicate
that the target device or a rectifier of the target device is
recognized to be in an open state, i.e., turned on.
[0076] For example, in the initial condition, the matching network
may be designed to maintain an input impedance of a source
resonator to remain in a first quadrant or a fourth quadrant of a
Smith chart. In another example, based on an operation
characteristic of a power amplifier in a power converter of the
source device, the input impedance of the source resonator may be
maintained to remain in quadrants other than the first quadrant and
the fourth quadrant of the Smith chart. For example, in the initial
condition, if the input impedance of the source resonator remains
in a second quadrant based on the operation characteristic of the
power amplifier, a larger amount of power is transferred to the
target device. Condition 3 will be further described with reference
to FIG. 11.
[0077] In the wireless power transmission system, a matching
network performs impedance matching. Various impedance matching
schemes may exist, and will be described with reference to examples
below.
[0078] FIGS. 3 through 5 illustrate examples of schemes of
adjusting an impedance between a source resonator and a target
resonator. Referring to FIG. 3, an impedance between a source
resonator 320 and a target resonator 340 may be adjusted based on
sizes of feeders 310 and 330, and a distance between the source
resonator 320 and the target resonator 340.
[0079] However, it is difficult to perform impedance matching in
real time based on the sizes of the feeders 310 and 330, and the
distance between the source resonator 320 and the target resonator
340. Accordingly, the impedance matching may need to be performed
adaptively based on a change in impedance, using a matching
network.
[0080] Referring to FIG. 4, impedance matching between a source
resonator 420 and a target resonator 440 may be performed using
matching networks (M/N) 430 and 460 respectively connected to
feeders 410 and 450. For example, an impedance between the source
resonator 420 and the target resonator 440 may be changed based on
a change in a load (Z.sub.L) 470. In this example, each of the
matching networks 430 and 460 includes an adaptive circuit
configured to perform impedance matching adaptively based on a
change in the impedance between the source resonator 420 and the
target resonator 440.
[0081] The adaptive circuit may include, for example, a circuit
configured to turn on an element, such as a capacitor or an
inductor, using switches. The switches may include, for example,
electrical switches, microelectromechanical systems (MEMS)
switches, and/or relay switches. Additionally, the adaptive circuit
may include a resonance transmission line, and/or an active
element, such as, for example, a varactor.
[0082] As described above, a wide variety of schemes may be used to
adaptively perform impedance matching. However, the impedance
matching needs to be performed to satisfy condition 2.
[0083] For convenience of description, for example, when a source
device determines a VSWR in real time, and the VSWR is greater than
2, a capacitance or an inductance of a matching network may be
changed. That is, a capacitance value or an inductance value of the
matching network may be determined to maintain the VSWR to be less
than 2, while continuing to change the capacitance or the
inductance.
[0084] In this example, the source device may determine the VSWR
using a reflected wave. Additionally, the source device and a
target device may transmit and receive information used to
determine the VSWR via communication.
[0085] Referring to FIG. 5, matching networks (M/N) 520 and 540 are
connected directly to a source resonator 510 and a target resonator
530, respectively. An impedance between the source resonator 510
and the target resonator 530 may be changed based on various causes
and/or a change in a load (Z.sub.L) 550. Similarly to the matching
networks 430 and 460 of FIG. 4, each of the matching networks 520
and 540 includes an adaptive circuit configured to perform
impedance matching adaptively based on a change in the impedance
between the source resonator 510 and the target resonator 530.
[0086] FIGS. 6A and 6B are diagrams illustrating an example of a
wireless power transmitter. Referring to FIG. 6A, the wireless
power transmitter includes a source resonator 610 and a feeding
unit 620. The source resonator 610 further includes a capacitor
611. The feeding unit 620 is electrically connected to both ends of
the capacitor 611.
[0087] FIG. 6B illustrates, in greater detail, a structure of the
wireless power transmitter of FIG. 6A. The source resonator 610
includes a first transmission line (not identified by a reference
numeral in FIG. 6B, but formed by various elements in FIG. 6B as
discussed below), a first conductor 641, a second conductor 642,
and at least one capacitor 650.
[0088] The capacitor 650 is inserted in series between a first
signal conducting portion 631 and a second signal conducting
portion 632, causing an electric field to be confined within the
capacitor 650. Generally, a transmission line includes at least one
conductor in an upper portion of the transmission line, and at
least one conductor in a lower portion of first transmission line.
A current may flow through the at least one conductor disposed in
the upper portion of the first transmission line, and the at least
one conductor disposed in the lower portion of the first
transmission line may be electrically grounded. In this example, a
conductor disposed in an upper portion of the first transmission
line in FIG. 6B is separated into two portions that will be
referred to as the first signal conducting portion 631 and the
second signal conducting portion 632. A conductor disposed in a
lower portion of the first transmission line in FIG. 6B will be
referred to as a first ground conducting portion 633.
[0089] As illustrated in FIG. 6B, the source resonator 610 has a
generally two-dimensional (2D) structure. The first transmission
line includes the first signal conducting portion 631 and the
second signal conducting portion 632 in the upper portion of the
first transmission line, and includes the first ground conducting
portion 633 in the lower portion of the first transmission line.
The first signal conducting portion 631 and the second signal
conducting portion 632 are disposed to face the first ground
conducting portion 633. A current flows through the first signal
conducting portion 631 and the second signal conducting portion
632.
[0090] One end of the first signal conducting portion 631 is
connected to one end of the first conductor 641, the other end of
the first signal conducting portion 631 is connected to the
capacitor 650, and the other end of the first conductor 641 is
connected to one end of the first ground conducting portion 633.
One end of the second signal conducting portion 632 is connected to
one end of the second conductor 642, the other end of the second
signal conducting portion 632 is connected to the other end of the
capacitor 650, and the other end of the second conductor 642 is
connected to the other end of the ground conducting portion 633.
Accordingly, the first signal conducting portion 631, the second
signal conducting portion 632, the first ground conducting portion
633, the first conductor 641, and the second conductor 642 are
connected to each other, causing the source resonator 610 to have
an electrically closed loop structure. The term "loop structure"
includes a polygonal structure, a circular structure, a rectangular
structure, and any other geometrical structure that is closed,
i.e., that does not have any opening in its perimeter. The
expression "having a loop structure" indicates a structure that is
electrically closed.
[0091] The capacitor 650 is inserted into an intermediate portion
of the first transmission line. In the example in FIG. 6B, the
capacitor 650 is inserted into a space between the first signal
conducting portion 631 and the second signal conducting portion
632. The capacitor 650 may be a lumped element capacitor, a
distributed capacitor, or any other type of capacitor known to one
of ordinary skill in the art. For example, a distributed element
capacitor may include a zigzagged conductor line and a dielectric
material having a relatively high permittivity disposed between
parallel portions of the zigzagged conductor line.
[0092] The capacitor 650 inserted into the first transmission line
may cause the source resonator 610 to have a characteristic of a
metamaterial. A metamaterial is a material having a predetermined
electrical property that is not found in nature, and thus may have
an artificially designed structure. All materials existing in
nature have a magnetic permeability and permittivity. Most
materials have a positive magnetic permeability and/or a positive
permittivity.
[0093] For most materials, a right-hand rule may be applied to an
electric field, a magnetic field, and a Poynting vector of the
materials, so the materials may be referred to as right-handed
materials (RHMs). However, a metamaterial that has a magnetic
permeability and/or a permittivity that is not found in nature, and
may be classified into an epsilon negative (ENG) material, a mu
negative (MNG) material, a double negative (DNG) material, a
negative refractive index (NRI) material, a left-handed (LH)
material, and other metamaterial classifications known to one of
ordinary skill in the art based on a sign of the magnetic
permeability of the metamaterial and a sign of the permittivity of
the metamaterial.
[0094] If the capacitor 650 is a lumped element capacitor and a
capacitance of the capacitor 650 is appropriately determined, the
source resonator 610 may have a characteristic of a metamaterial.
If the source resonator 610 is caused to have a negative magnetic
permeability by appropriately adjusting the capacitance of the
capacitor 650, the source resonator 610 may also be referred to as
an MNG resonator. Various criteria may be applied to determine the
capacitance of the capacitor 650. For example, the various criteria
may include a criterion for enabling the source resonator 610 to
have the characteristic of the metamaterial, a criterion for
enabling the source resonator 610 to have a negative magnetic
permeability at a target frequency, a criterion for enabling the
source resonator 610 to have a zeroth order resonance
characteristic at the target frequency, and any other suitable
criterion. Based on any one or any combination of the
aforementioned criteria, the capacitance of the capacitor 650 may
be appropriately determined.
[0095] The source resonator 610, hereinafter referred to as the MNG
resonator 610, may have a zeroth order resonance characteristic of
having a resonance frequency when a propagation constant is "0". If
the MNG resonator 610 has the zeroth order resonance
characteristic, the resonance frequency is independent of a
physical size of the MNG resonator 610. By changing the capacitance
of the capacitor 650, the resonance frequency of the MNG resonator
610 may be changed without changing the physical size of the MNG
resonator 610.
[0096] In a near field, the electric field is concentrated in the
capacitor 650 inserted into the first transmission line, causing
the magnetic field to become dominant in the near field. The MNG
resonator 610 has a relatively high Q-factor when the capacitor 650
is a lumped element, thereby increasing a power transmission
efficiency. The Q-factor indicates a level of an ohmic loss or a
ratio of a reactance with respect to a resistance in the wireless
power transmission. As will be understood by one of ordinary skill
in the art, the efficiency of the wireless power transmission will
increase as the Q-factor increases.
[0097] Although not illustrated in FIG. 6B, a magnetic core passing
through the MNG resonator 610 may be provided to increase a power
transmission distance.
[0098] Referring to FIG. 6B, the feeding unit 620 includes a second
transmission line (not identified by a reference numeral in FIG.
6B, but formed by various elements in FIG. 6B as discussed below),
a third conductor 671, a fourth conductor 672, a fifth conductor
681, and a sixth conductor 682.
[0099] The second transmission line includes a third signal
conducting portion 661 and a fourth signal conducting portion 662
in an upper portion of the second transmission line, and includes a
second ground conducting portion 663 in a lower portion of the
second transmission line. The third signal conducting portion 661
and the fourth signal conducting portion 662 are disposed to face
the second ground conducting portion 663. A current flows through
the third signal conducting portion 661 and the fourth signal
conducting portion 662.
[0100] One end of the third signal conducting portion 661 is
connected to one end of the third conductor 671, the other end of
the third signal conducting portion 661 is connected to one end of
the fifth conductor 681, and the other end of the third conductor
671 is connected to one end of the second ground conducting portion
663. One end of the fourth signal conducting portion 662 is
connected to one end of the fourth conductor 672, the other end of
the fourth signal conducting portion 662 is connected to one end
the sixth conductor 682, and the other end of the fourth conductor
672 is connected to the other end of the second ground conducting
portion 663. The other end of the fifth conductor 681 is connected
to the first signal conducting portion 631 at or near where the
first signal conducting portion 631 is connected to one end of the
capacitor 650, and the other end of the sixth conductor 682 is
connected to the second signal conducting portion 632 at or near
where the second signal conducting portion 632 is connected to the
other end of the capacitor 650. Thus, the fifth conductor 681 and
the sixth conductor 682 are connected in parallel to both ends of
the capacitor 650. The fifth conductor 681 and the sixth conductor
682 are used as an input port to receive an RF signal as an
input.
[0101] Accordingly, the third signal conducting portion 661, the
fourth signal conducting portion 662, the second ground conducting
portion 663, the third conductor 671, the fourth conductor 672, the
fifth conductor 681, the sixth conductor 682, and the source
resonator 610 are connected to each other, causing the source
resonator 610 and the feeding unit 620 to have an electrically
closed loop structure. The term "loop structure" includes a
polygonal structure, a circular structure, a rectangular structure,
and any other geometrical structure that is closed, i.e., that does
not have any opening in its perimeter. The expression "having a
loop structure" indicates a structure that is electrically
closed.
[0102] If an RF signal is input to the fifth conductor 681 or the
sixth conductor 682, input current flows through the feeding unit
620 and the source resonator 610, generating a magnetic field that
induces a current in the source resonator 610. A direction of the
input current flowing through the feeding unit 620 is identical to
a direction of the induced current flowing through the source
resonator 610, thereby causing a strength of a total magnetic field
to increase in the center of the source resonator 610, and decrease
near the outer periphery of the source resonator 610.
[0103] An input impedance is determined by an area of a region
between the source resonator 610 and the feeding unit 620.
Accordingly, a separate matching network used to match the input
impedance to an output impedance of a power amplifier may not be
necessary. However, if a matching network is used, the input
impedance may be adjusted by adjusting a size of the feeding unit
620, and accordingly a structure of the matching network may be
simplified. The simplified structure of the matching network may
reduce a matching loss of the matching network.
[0104] The second transmission line, the third conductor 671, the
fourth conductor 672, the fifth conductor 681, and the sixth
conductor 682 of the feeding unit may have a structure identical to
the structure of the source resonator 610. For example, if the
source resonator 610 has a loop structure, the feeding unit 620 may
also have a loop structure. As another example, if the source
resonator 610 has a circular structure, the feeding unit 620 may
also have a circular structure.
[0105] The configuration of the source resonator 610 and the
configuration of the feeding unit 620, as described above, may
equally be applied to a target resonator and a feeding unit of the
target resonator, of a wireless power receiver.
[0106] FIG. 7A is a diagram illustrating an example of a
distribution of a magnetic field within a source resonator based on
feeding of a feeding unit. FIG. 7A more simply illustrates the
source resonator 610 and the feeding unit 620 of FIGS. 6A and 6B,
and the names of the various elements in FIG. 6B will be used in
the following description of FIG. 7A without reference
numerals.
[0107] A feeding operation may be an operation of supplying power
to a source resonator in wireless power transmission, or an
operation of supplying AC power to a rectification unit in wireless
power transmission. FIG. 7A illustrates a direction of input
current flowing in the feeding unit, and a direction of induced
current flowing in the source resonator. Additionally, FIG. 7A
illustrates a direction of a magnetic field formed by the input
current of the feeding unit, and a direction of a magnetic field
formed by the induced current of the source resonator.
[0108] Referring to FIG. 7A, the fifth conductor or the sixth
conductor of the feeding unit 620 may be used as an input port 710.
In FIG. 7A, the sixth conductor of the feeding unit is being used
as the input port 710. An RF signal is input to the input port 710.
The RF signal may be output from a power amplifier. The power
amplifier may increase and decrease an amplitude of the RF signal
based on a power requirement of a target device. The RF signal
input to the input port 710 is represented in FIG. 7A as an input
current flowing in the feeding unit. The input current flows in a
clockwise direction in the feeding unit along the second
transmission line of the feeding unit. The fifth conductor and the
sixth conductor of the feeding unit are electrically connected to
the source resonator. More specifically, the fifth conductor of the
feeding unit is connected to the first signal conducting portion of
the source resonator, and the sixth conductor of the feeding unit
is connected to the second signal conducting portion of the source
resonator. Accordingly, the input current flows in both the source
resonator and the feeding unit. The input current flows in a
counterclockwise direction in the source resonator along the first
transmission line of the source resonator. The input current
flowing in the source resonator generates a magnetic field, and the
magnetic field induces a current in the source resonator due to the
magnetic field. The induced current flows in a clockwise direction
in the source resonator along the first transmission line of the
source resonator. The induced current in the source resonator
transfers energy to the capacitor of the source resonator, and also
generates a magnetic field. In FIG. 7A, the input current flowing
in the feeding unit and the source resonator is indicated by solid
lines with arrowheads, and the induced current flowing in the
source resonator is indicated by dashed lines with arrowheads.
[0109] A direction of a magnetic field generated by a current is
determined based on the right-hand rule. As illustrated in FIG. 7A,
within the feeding unit, a direction 721 of the magnetic field
generated by the input current flowing in the feeding unit is
identical to a direction 723 of the magnetic field generated by the
induced current flowing in the source resonator. Accordingly, a
strength of the total magnetic field may increases inside the
feeding unit.
[0110] In contrast, as illustrated in FIG. 7A, in a region between
the feeding unit and the source resonator, a direction 733 of the
magnetic field generated by the input current flowing in the
feeding unit is opposite to a direction 731 of the magnetic field
generated by the induced current flowing in the source resonator.
Accordingly, the strength of the total magnetic field decreases in
the region between the feeding unit and the source resonator.
[0111] Typically, in a source resonator having a loop structure, a
strength of a magnetic field decreases in the center of the source
resonator, and increases near an outer periphery of the source
resonator. However, referring to FIG. 7A, since the feeding unit is
electrically connected to both ends of the capacitor of the source
resonator, the direction of the induced current in the source
resonator is identical to the direction of the input current in the
feeding unit. Since the direction of the induced current in the
source resonator is identical to the direction of the input current
in the feeding unit, the strength of the total magnetic field
increases inside the feeding unit, and decreases outside the
feeding unit. As a result, due to the feeding unit, the strength of
the total magnetic field increases in the center of the source
resonator having the loop structure, and decreases near an outer
periphery of the source resonator, thereby compensating for the
normal characteristic of the source resonator having the loop
structure in which the strength of the magnetic field decreases in
the center of the source resonator, and increases near the outer
periphery of the source resonator. Thus, the strength of the total
magnetic field may be constant inside the source resonator.
[0112] A power transmission efficiency for transferring wireless
power from a source resonator to a target resonator is proportional
to the strength of the total magnetic field generated in the source
resonator. Accordingly, when the strength of the total magnetic
field increases inside the source resonator, the power transmission
efficiency also increases.
[0113] FIG. 7B is a diagram illustrating examples of equivalent
circuits of a feeding unit and a source resonator. Referring to
FIG. 7B, a feeding unit 740 and a source resonator 750 may be
represented by the equivalent circuits in FIG. 7B. The feeding unit
740 is represented as an inductor having an inductance L.sub.f, and
the source resonator 750 is represented as a series connection of
an inductor having an inductance L coupled to the inductance
L.sub.f of the feeding unit 740 by a mutual inductance M, a
capacitor having a capacitance C, and a resistor having a
resistance R. An example of an input impedance Z.sub.in viewed in a
direction from the feeding unit 740 to the source resonator 750 may
be expressed by the following Equation 4:
Z in = ( .omega. M ) 2 Z ( 1 ) ##EQU00001##
[0114] In Equation 4, M denotes a mutual inductance between the
feeding unit 740 and the source resonator 750, .omega. denotes a
resonance frequency of the feeding unit 740 and the source
resonator 750, and Z denotes an impedance viewed in a direction
from the source resonator 750 to a target device. As can be seen
from Equation 4, the input impedance Z.sub.in is proportional to
the square of the mutual inductance M. Accordingly, the input
impedance Z.sub.in may be adjusted by adjusting the mutual
inductance M. The mutual inductance M depends on an area of a
region between the feeding unit 740 and the source resonator 750.
The area of the region between the feeding unit 740 and the source
resonator 750 may be adjusted by adjusting a size of the feeding
unit 740, thereby adjusting the mutual inductance M and the input
impedance Z.sub.in.
[0115] In a target resonator and a feeding unit included in a
wireless power receiver, a magnetic field may be distributed as
illustrated in FIG. 7A. For example, the target resonator may
receive wireless power from a source resonator via magnetic
coupling. The received wireless power induces a current in the
target resonator. The induced current in the target resonator
generates a magnetic field, which induces a current in the feeding
unit. If the target resonator is connected to the feeding unit as
illustrated in FIG. 7A, a direction of the induced current flowing
in the target resonator will be identical to a direction of the
induced current flowing in the feeding unit. Accordingly, for the
reasons discussed above in connection with FIG. 7A, a strength of
the total magnetic field will increase inside the feeding unit, and
will decrease in a region between the feeding unit and the target
resonator.
[0116] FIGS. 8 and 9 illustrate examples of impedance matching of a
wireless power transmission system. Referring to FIG. 8, Z.sub.in
indicates an input impedance of a source resonator 820, Z.sub.2
indicates an impedance between a feeder 810 of the source resonator
820 and the source resonator 820, and Z.sub.1 indicates an
impedance between the source resonator 820 and a target resonator
830.
[0117] The impedances Z.sub.1 and Z.sub.2 may be expressed by the
following Equations 2 and 3:
Z 1 .apprxeq. R t + .omega. 2 M tof 2 R o + Z L ( 2 ) Z 2 = R s +
.omega. 2 M st 2 Z 2 ( 3 ) ##EQU00002##
[0118] In Equations 2 and 3, R.sub.t denotes a resistance of the
target resonator 830, denotes an angular speed of a resonance
frequency, M.sub.tof denotes a mutual inductance between a feeder
840 of the target resonator 830 and the target resonator 830,
R.sub.o denotes a resistance of the feeder 840, R.sub.S denotes a
resistance of the source resonator 820, and M.sub.st denotes a
mutual inductance between the source resonator 820 and the target
resonator 830.
[0119] The input impedance Z.sub.in may be expressed by the
following Equation 4:
Z in .apprxeq. R i + .omega. 2 M ifs 2 Z 2 ( 4 ) ##EQU00003##
[0120] In Equation 4, R.sub.i denotes a resistance of the feeder
810, and M.sub.ifs denotes a mutual inductance between the feeder
810 and the source resonator 820.
[0121] FIG. 9 illustrates impedances associated with a target
device. In FIG. 9, Z'.sub.in indicates an output impedance of a
target resonator 920, Z'.sub.2 indicates an impedance between a
feeder 910 of the target resonator 920 and the target resonator
920, and Z'.sub.1 indicates an impedance between a source resonator
930 and the target resonator 920.
[0122] The impedances Z'.sub.1, Z'.sub.2, and Z'.sub.in associated
with the target device may be expressed by the following Equations
5 through 7:
Z 1 ' = R s + .omega. 2 M ifs 2 R i + Z S ( 5 ) Z 2 ' = R t +
.omega. 2 M st 2 Z 1 ' ( 6 ) Z in ' = R o + .omega. 2 M tof 2 Z 2 '
( 7 ) ##EQU00004##
[0123] In Equations 5 through 7, Z.sub.S denotes an impedance of a
source device connected to a feeder 940.
[0124] Referring to Equations 2 through 7, impedance parameters of
a wireless power transmission system may be generally determined
based on a size of a feeder, a distance between a feeder and a
resonator, a distance between resonators, and a load Z.sub.L of a
target device. Additionally, a resistance of a source resonator
and/or a target resonator may be ignored due to an extremely small
value of the resistance.
[0125] FIG. 10 illustrates an example of a matching network of a
wireless power transmission system. Referring to FIG. 10, the
wireless power transmission system includes a wireless power link
1030, a matching network 1010 of a source device, and a matching
network 1020 of a target device.
[0126] The matching network 1010 is represented as a series
connection of a capacitor including a capacitance C.sub.1, and an
inductor including an inductance of L.sub.1, and the capacitor, the
inductor, and the wireless power link 1030 are connected to each
other at a node. The matching network 1020 is represented as a
series connection of a capacitor including a capacitance C.sub.2,
and an inductor including an inductance of L.sub.2, and the
capacitor, the inductor, and the wireless power link 1030 are
connected to each other at an opposite node. The matching networks
1010 and 1020 include input impedances Z.sub.in and Z'.sub.in,
respectively.
[0127] A predetermined ITR (e.g., close to a value of 1) may be
applied to the target device, as well as the source device. In an
example in which the ITR includes a minimum value, a total
efficiency of the wireless power transmission system may increase.
In another example in which a value of the ITR is less than or
equal to 1, functions of the matching networks 1010 and 1020 may
hardly be performed, and power dissipated by the matching networks
1010 and 1020 may be close to a value of 0.
[0128] If condition 2 is satisfied, and the ITR includes a large
value, an intensity of current flowing in the matching networks
1010 and 1020 may increase. Accordingly, an element including one
of the matching networks 1010 and 1020 may cause a loss in the
total efficiency.
[0129] To satisfy condition 2, the matching networks 1010 and 1020
may perform impedance matching adaptively based on a change in an
impedance between a source resonator of the source device and the
target device. Additionally, to satisfy condition 2, the matching
networks 1010 and 1020 may adaptively perform the impedance
matching to maintain a value of a VSWR between the source resonator
and the target device to be less than 2.
[0130] The matching network 1010 may be designed or configured to
maintain the input impedance Z.sub.in of the source resonator to
remain in a first quadrant or a fourth quadrant of a Smith chart,
in an initial condition. The initial condition may indicate that
the target device or a rectifier of the target device is recognized
to be in an open state. Hereinafter, the initial condition will be
further described with reference to FIG. 11.
[0131] FIG. 11 illustrates an example of a Smith chart to describe
an impedance matching condition of a wireless power transmission
system. Referring to FIG. 11, the Smith chart is divided into a
first quadrant 1110, a second quadrant 1130, a third quadrant 1140,
and a fourth quadrant 1120 based on positions of distributed
impedances.
[0132] In an example in which an input impedance of a source
resonator is positioned in the first quadrant 1110 or the fourth
quadrant 1120, as indicated by a circle 1160, a source device
transmits high power to a target device, and condition 3 is
satisfied. In this example, a distribution of contour lines 1161,
1162, 1163 and 1164 indicates that an amount of the power
transmitted to the target device increases as a distance between
the circle 1160 and each of the contour lines 1161, 1162, 1163 and
1164 decreases.
[0133] In another example in which the input impedance of the
source resonator is positioned around a circle 1150 (e.g., in the
second quadrant 1130), a power transmission efficiency may
increase, and condition 3 may be satisfied. In this example, a
distribution of contour lines 1151, 1152 and 1153 indicates that
the power transmission efficiency increases as a distance between
the circle 1150 and each of the contour lines 1151, 1152 and 1153
decreases.
[0134] For example, when a resonance is initialized between the
source resonator and a target resonator, a rectifier of the target
device may include an extremely high impedance. When a
predetermined period of time elapses after the resonance is
initialized, power is supplied to the rectifier, and the rectifier
is turned on. Accordingly, in an initial condition, a matching
network of the source device may need to be designed or configured
so that a large amount of power is transferred to the target
device. Furthermore, when the rectifier is turned on, the matching
network may need to be designed or configured to satisfy condition
2. In other words, condition 3 may refer to a design condition of
the matching network to satisfy condition 2 when the rectifier is
turned on.
[0135] In an example in which the input impedance of the source
resonator is maintained to remain in the first quadrant 1110 or the
fourth quadrant 1120 of the Smith chart, in the initial condition,
when the rectifier is turned on, condition 2 is satisfied. In
another example in which the input impedance of the source
resonator is positioned in a dotted circle 1101 or 1102, in the
initial condition, when the rectifier is turned on, condition 2 is
satisfied.
[0136] Schemes of positioning the input impedance of the source
resonator in the first quadrant 1110 or the fourth quadrant 1120 in
the initial condition may be combined in various combinations. For
example, a value satisfying condition 3 may be determined by
properly adjusting a resistance value of the input impedance of the
source resonator. Additionally, based on an operation
characteristic of a power amplifier in a power converter of the
source device, the input impedance of the source resonator may be
maintained to remain in quadrants other than the first quadrant
1110 and the fourth quadrant 1120 (e.g., the second quadrant 1130)
of the Smith chart.
[0137] According to the teachings above, there is provided a
wireless power transmission system maintaining a power transmission
efficiency. Additionally, there is provided an operation condition
of a source device and an operation condition of a target device
that enables efficient impedance matching. Furthermore, there is
provided a source device and a target device achieving a high power
transmission efficiency in a multi-target environment.
[0138] FIG. 12 illustrates an example of an electric vehicle
charging system. Referring to FIG. 12, an electric vehicle charging
system 1200 includes a source system 1210, a source resonator 1220,
a target resonator 1230, a target system 1240, and an electric
vehicle battery 1250.
[0139] In one example, the electric vehicle charging system 1200
has a structure similar to the structure of the wireless power
transmission system of FIG. 1. The source system 1210 and the
source resonator 1220 in the electric vehicle charging system 1200
operate as a source. The target resonator 1230 and the target
system 1240 in the electric vehicle charging system 1200 operate as
a target.
[0140] In one example, the source system 1210 includes an
alternating current-to-direct current (AC/DC) converter, a power
detector, a power converter, a control and communication
(control/communication) unit similar to those of the source device
110 of FIG. 1. In one example, the target system 1240 includes a
rectification unit, a DC-to-DC (DC/DC) converter, a switch unit, a
charging unit, and a control/communication unit similar to those of
the target device 120 of FIG. 1. The electric vehicle battery 1250
is charged by the target system 1240. The electric vehicle charging
system 1200 may use a resonance frequency in a band of a few kHz to
tens of MHz.
[0141] The source system 1210 generates power based on a type of
the vehicle being charged, a capacity of the electric vehicle
battery 1250, and a charging state of the electric vehicle battery
1250, and wirelessly transmits the generated power to the target
system 1240 via a magnetic coupling between the source resonator
1220 and the target resonator 1230.
[0142] The source system 1210 may control an alignment of the
source resonator 1220 and the target resonator 1230. For example,
when the source resonator 1220 and the target resonator 1230 are
not aligned, the controller of the source system 1210 may transmit
a message to the target system 1240 to control the alignment of the
source resonator 1220 and the target resonator 1230.
[0143] For example, when the target resonator 1230 is not located
in a position enabling maximum magnetic coupling, the source
resonator 1220 and the target resonator 1230 are not properly
aligned. When a vehicle does not stop at a proper position to
accurately align the source resonator 1220 and the target resonator
1230, the source system 1210 may instruct a position of the vehicle
to be adjusted to control the source resonator 1220 and the target
resonator 1230 to be aligned. However, this is just an example, and
other methods of aligning the source resonator 1220 and the target
resonator 1230 may be used.
[0144] The source system 1210 and the target system 1240 may
transmit or receive an ID of a vehicle and exchange various
messages by performing communication with each other.
[0145] The descriptions of FIGS. 2 through 11 are also applicable
to the electric vehicle charging system 1200. However, the electric
vehicle charging system 1200 may use a resonance frequency in a
band of a few kHz to tens of MHz, and may wirelessly transmit power
that is equal to or higher than tens of watts to charge the
electric vehicle battery 1250.
[0146] FIGS. 13A through 14B illustrate examples of applications in
which a wireless power receiver and a wireless power transmitter
are mounted. FIG. 13A illustrates an example of wireless power
charging between a pad 1310 and a mobile terminal 1320, and FIG.
13B illustrates an example of wireless power charging between pads
1330 and 1340 and hearing aids 1350 and 1360, respectively.
[0147] Referring to FIG. 13A, a wireless power transmitter is
mounted in the pad 1310, and a wireless power receiver is mounted
in the mobile terminal 1320. The pad 1310 charges a single mobile
terminal, namely, the mobile terminal 1320.
[0148] Referring to FIG. 13B, two wireless power transmitters are
respectively mounted in the pads 1330 and 1340. The hearing aids
1350 and 1360 are used for a left ear and a right ear,
respectively. Two wireless power receivers are respectively mounted
in the hearing aids 1350 and 1360. The pads 1330 and 1340 charge
two hearing aids, respectively, namely, the hearing aids 1350 and
1360.
[0149] FIG. 14A illustrates an example of wireless power charging
between an electronic device 1410 inserted into a human body, and a
mobile terminal 1420. FIG. 14B illustrates an example of wireless
power charging between a hearing aid 1430 and a mobile terminal
1440.
[0150] Referring to FIG. 14A, a wireless power transmitter and a
wireless power receiver are mounted in the mobile terminal 1420.
Another wireless power receiver is mounted in the electronic device
1410. The electronic device 1410 is charged by receiving power from
the mobile terminal 1420.
[0151] Referring to FIG. 14B, a wireless power transmitter and a
wireless power receiver are mounted in the mobile terminal 1440.
Another wireless power receiver is mounted in the hearing aid 1430.
The hearing aid 1430 is charged by receiving power from the mobile
terminal 1440. Low-power electronic devices, for example, Bluetooth
earphones, may also be charged by receiving power from the mobile
terminal 1440.
[0152] FIG. 15 illustrates an example of a wireless power
transmitter and a wireless power receiver. Referring to FIG. 15, a
wireless power transmitter 1510 may be mounted in each of the pad
1310 of FIG. 13A and pads 1330 and 1340 of FIG. 13B. Additionally,
the wireless power transmitter 1510 may be mounted in each of the
mobile terminal 1420 of FIG. 14A and the mobile terminal 1440 of
FIG. 14B.
[0153] In addition, a wireless power receiver 1520 may be mounted
in each of the mobile terminal 1320 of FIG. 13A and the hearing
aids 1350 and 1360 of FIG. 13B. Further, the wireless power
receiver 1520 may be mounted in each of the electronic device 1410
of FIG. 14A and the hearing aid 1430 of FIG. 14B.
[0154] The wireless power transmitter 1510 may include a similar
configuration to the source device 110 of FIG. 1. For example, the
wireless power transmitter 1510 may include a unit configured to
transmit power using magnetic coupling.
[0155] Referring to FIG. 15, the wireless power transmitter 1510
includes a signal generator, a power amplifier, a microcontroller
unit (MCU), a source resonator, and a communication/tracking unit
1511. The communication/tracking unit 1511 communicates with the
wireless power receiver 1520, and controls an impedance and a
resonance frequency to maintain a wireless power transmission
efficiency. Additionally, the communication/tracking unit 1511 may
perform similar functions to the power converter 114 and the
control/communication unit 115 of FIG. 1.
[0156] The wireless power receiver 1520 may include a similar
configuration to the target device 120 of FIG. 1. For example, the
wireless power receiver 1520 may include a unit configured to
wirelessly receive power and to charge a battery.
[0157] Referring to FIG. 15, the wireless power receiver 1520
includes a target resonator, a rectifier, a DC/DC converter, and a
charging circuit. Additionally, the wireless power receiver 1520
includes a communication/control unit 1523. The
communication/control unit 1523 communicates with the wireless
power transmitter 1510, and performs an operation to protect
overvoltage and overcurrent.
[0158] The wireless power receiver 1520 may include a hearing
device circuit 1521. The hearing device circuit 1521 may be charged
by a battery. The hearing device circuit 1521 may include a
microphone, an analog-to-digital converter (ADC), a processor, a
digital-to-analog converter (DAC), and a receiver. For example, the
hearing device circuit 1521 may include the same configuration as a
hearing aid.
[0159] The units described herein may be implemented using hardware
components, software components, or a combination thereof. For
example, the hardware components may include microphones,
amplifiers, band-pass filters, audio to digital convertors, and
processing devices. A processing device may be implemented using
one or more general-purpose or special purpose computers, such as,
for example, a processor, a controller and an arithmetic logic
unit, a digital signal processor, a microcomputer, a field
programmable array, a programmable logic unit, a microprocessor or
any other device capable of responding to and executing
instructions in a defined manner. The processing device may run an
operating system (OS) and one or more software applications that
run on the OS. The processing device also may access, store,
manipulate, process, and create data in response to execution of
the software. For purpose of simplicity, the description of a
processing device is used as singular; however, one skilled in the
art will appreciated that a processing device may include multiple
processing elements and multiple types of processing elements. For
example, a processing device may include multiple processors or a
processor and a controller. In addition, different processing
configurations are possible, such as parallel processors.
[0160] The software may include a computer program, a piece of
code, an instruction, or some combination thereof, to independently
or collectively instruct or configure the processing device to
operate as desired. Software and data may be embodied permanently
or temporarily in any type of machine, component, physical or
virtual equipment, computer storage medium or device, or in a
propagated signal wave capable of providing instructions or data to
or being interpreted by the processing device. The software also
may be distributed over network coupled computer systems so that
the software is stored and executed in a distributed fashion. The
software and data may be stored by one or more computer readable
recording mediums. The computer readable recording medium may
include any data storage device that can store data which can be
thereafter read by a computer system or processing device. Examples
of the non-transitory computer readable recording medium include
read-only memory (ROM), random-access memory (RAM), CD-ROMs,
magnetic tapes, floppy disks, optical data storage devices. Also,
functional programs, codes, and code segments accomplishing the
examples disclosed herein can be easily construed by programmers
skilled in the art to which the examples pertain based on and using
the flow diagrams and block diagrams of the figures and their
corresponding descriptions as provided herein.
[0161] As a non-exhaustive illustration only, a terminal and a
device described herein may refer to mobile devices such as a
cellular phone, a personal digital assistant (PDA), a digital
camera, a portable game console, and an MP3 player, a
portable/personal multimedia player (PMP), a handheld e-book, a
portable laptop PC, a global positioning system (GPS) navigation, a
tablet, a sensor, and devices such as a desktop PC, a high
definition television (HDTV), an optical disc player, a setup box,
a home appliance, and the like that are capable of wireless
communication or network communication consistent with that which
is disclosed herein.
[0162] A number of examples have been described above.
Nevertheless, it will be understood that various modifications may
be made. For example, suitable results may be achieved if the
described techniques are performed in a different order and/or if
components in a described system, architecture, device, or circuit
are combined in a different manner and/or replaced or supplemented
by other components or their equivalents. Accordingly, other
implementations are within the scope of the following claims.
* * * * *